how to compare similar column names in two tables

Question

I have two tables.

Faculty_Code   Text (Table Name Faculty_Details)

Records in the Faculty_Details as follows;

Faculty_Code 

GS

MK

CK

NR

Another Table (Table Name  Schedule_Details)

Faculty_Code

GS

Mk

SJ

PN

then in the run mode in the combo box all the Faculty_Code from Faculty_Details( table) will display in the combo box.

in combo box  Faculty_Code  as follows from the table  Faculty_Details.

GS

MK

CK

NR

Then i have one button called   View.

when  user select   Faculty_Code GS (the Gs Faculty_Code is there in the both the table) from  the combo box and click the view button.

i want to show the message the select faculty is there.please select different faculty.

how can i show the pop up message using c sharp.